1. Field of the Invention
The present invention relates to damping valves, specifically a damping valve arrangement for controlling a pilot pressure that exerts influence on a control chamber of a damping device of a vibration damper by means of a control fluid, with an armature that is displaceable by means of an electrically exercisable coil and provided in a housing. The armature comprises a guide pin on which a first spring washer is provided and braces the guide pin.
The invention further relates to a method for controlling a pilot pressure in a control chamber of a damping device of a vibration damper by means of a magnetically actuated armature of a valve arrangement, which armature changes the area of a flow-through opening in the valve arrangement, through which a control fluid flows.
2. Background Art
A pressure regulator for a valve of a shock absorber, in which a piston supported so as to be axially displaceable in two bushings is actuated by means of a solenoid, has been disclosed in patent publication WO 2009/157841 A1. In this case, the piston is supported on a spring washer that is able to generate an axial force but is unable to provide any radial guiding forces; radial guidance is provided by the two bushings. Consequently, when the piston is to be moved, the adhesion forces prevailing in the two bushings must first be overcome, leading to breakaway forces. This leads to the result that an undesirable hysteresis is created by an axially oscillating movement of the piston, hindering precise control of the displacement movement of the piston, and the breakaway forces also increase the inertia of the system in undesirable manner, which impedes rapid regulating movement.
A hydraulic vibration damper with adjustable damping force, which has a pressure regulating valve with a piston that is movable across a magnetic coil, has been disclosed in German patent publication DE 199 14 504 C5. In this case, the piston is guided inside a cylindrical sleeve, with the result that a movement of the piston again creates increased friction in the sleeve, which yet again leads to the problem of hysteresis and negatively affects the regulating speed of the system.
A shock absorber with adjustable damping force, in which the inertia of the piston in the pressure control valve (solenoid valve) is reducible, was disclosed in German patent application DE 10 2009 015 584 A1. In this context, the plunger is arranged in a bore so as to be guided by the wall. The arrangement of the plunger against the wall gives rise to adhesion effects due to friction, and the inertia of the system therefore cannot be reduced effectively.
A shock absorber with damping force control was disclosed in German patent application DE 10 2010 046 833 A1. The shock absorber is equipped with a solenoid that actuates a piston which is guided in a bore. Unavoidable eccentricities of the bore result in adhesion effects of the piston in the bore, and therewith again to the hysteresis problems described above. The eccentricity of the bore also causes the gap existing around the piston to assume variable values along the circumference of the piston between the outer wall of the piston and the inner wall of the bore; in the case of small gaps, this in turn causes the piston to become pressed against the bore due to magnetic force generated by the solenoid—which again increases the difficulties of breakaway forces and thus also the problem of hysteresis.
A guide diaphragm with crosspieces that is used in a valve arrangement with an excitation coil was disclosed in German patent DE 2 245 255 A1. In this context, the guide diaphragm serves to guide an armature in the radial and axial directions; said guide diaphragm performs no other function.
A controllable vibration damper comprising an electrically actuated magnet that actuates a control needle, which is able to block a flow-through area and uncover it again in continuously variable manner, was disclosed in German patent application DE 40 16 807 C2. A valve body is accommodated in a valve housing so as to be axially displaceable relative to the control needle, in such manner that the valve body is seated in a bore of the valve housing. In such arrangement, the control needle is designed to precede the valve body with regard to the axial movement thereof, so that the fluid flow of the main stage follows a fluid flow that fulfils a pilot function.
Finally, an adjustable damping valve device in which a set spring constructed as a disc guides an axle body in a valve housing was disclosed in German patent application DE 10 2011 075 909 A1. In this case, the set spring serves as a preloading member that acts on the axle body. The axle body is supported in a valve body that is accommodated in a guide bore of the valve housing. Here too, unavoidable eccentricities of the guide bore give rise to wall adhesion effects of the valve body with respect to the valve housing, and consequently to the hysteresis problems described previously.
Starting from the foregoing background, the object underlying the present invention for eliminating the drawbacks described is now to create a damping valve arrangement that permits precise, rapid control of the control pressure that acts on the control chamber, and also enables a predefined damping effect of a vibration damper in the event of any failure of the electrical power supply. A method for controlling a pilot pressure in a control chamber of a damping device in a vibration damper is also to be produced.